1. Field of Invention
In the attempt to develop new technologies for economical storage of energy and to find possible solutions to the storage of electrical energy, the sodium-sulfur battery is considered promising in that it offers many advantages. The operating principles as well as the unique advantages of the sodium-sulfur-solid electrolyte battery have been discussed by Marcoux and Seo, "Sodium-Sulfur Batteries", Advan. Chem. Ser. No. 140,216 (1975).
Sulfur which forms the cathode is a non-conductor and, therefore, means must be provided for the transfer of electrons to and from the sulfur on charging and discharging. In addition, conventional structural metals are susceptible to corrosive attack by the sulfur/polysulfide melt present in the sulfur electrode container.
While aluminum, for many reasons, is a desirable choice for use as the container material for the sodium//sulfur battery, aluminum forms sulfide layers with poor conductivity when exposed to sulfur/polysulfide melts. Therefore means must be provided for allowing for efficient, stable, lasting low resistance transmission of electricity from the sulfur electrode to the aluminum container or other external conductor.
2. Description of the Prior Art
Gadd, Nejedlik, and Graham, "Vacuum, Pack and Slurry Coating Processes for Coating Superalloys," Electrochem. Tech, 6 (9010, 307-315) 1968; Smialek, "Exploratory Study of Oxidation-Resistant Aluminized Slurry Coatings for IN-100 and WI-52 Superalloys" (NASA'TN'D'6321 (1971)), and Llewelyn, "Protection of Nickel-Base Alloys Against Sulfur Corrosion by Pack Aluminizing," Hot Corrosion Problems Associated with Gas Turbines, ASTM-STP-421 (September 1967) all teach the preparation of metal aluminide coatings and their application as protective coatings for superalloys in high temperature turbines.
The problems specific to the use of metallic components in sodium-sulfur batteries are described in U.S. Pat. No. 3,982,959. There have been attempts at various mechanical and chemical means for providing electrical transmission from the sulfur electrode to the aluminum container, such as those described in U.S. Pat. No. 4,053,689. See also U.S. Pat. No. 4,070,527.